This invention is directed to a soy hydrolysate low in both sodium and monosodium glutamate and to a process for preparing the same.
Hydrolyzed vegetable protein, sometimes referred to as HVP is utilized to enhance the flavor of a wide range of food products including, among others, soups, gravies, sauces, bouillon, salad dressings, snack foods, processed meats and canned meats. A commonly utilized base material for preparing these hydrolyzed vegetable proteins is the solids remaining from soy beans after they have been dehulled and deoiled. The soy material is converted to a hydrolyzed vegetable protein via acid hydrolysis or enzymatic hydrolysis conducted under acidic conditions. The hydrolyzed vegetable protein resulting from these hydrolysis typically has a very large percentage of salts therein, upwards of 50%, and further contains a high percentage of monosodium glutamate, about 10%, which is derived from glutamic acid liberated during the hydrolysis.
Hydrolyzed vegetable protein is utilized as an additive to certain canned meat products, as for instance canned tuna. The addition of hydrolyzed vegetable protein to canned tuna prevents the migration of natural juices and natural products that are soluble in these juices from the flesh of the tuna to the broth in the can. If hydrolyzed vegetable protein is not added as an additive to canned tuna, the migration of the natural juices and natural solubles from the flesh to the liquid contents of the can could resulted in a reaction between the interior metallic surface of the can and the tuna juices. The reaction between the can and the juices results in a metallic taste being imparted to the contents of the can including the tuna. By adding hydrolyzed vegetable protein to the contents of the canned tuna, the loss of the natural juices from the tuna flesh is inhibited and this in turn inhibits the transfer of a metallic taste to the tuna flesh. This ability to retard metallic taste in tuna has resulted in the wide spread use by the tuna canning industry of hydrolyzed vegetable protein as an additive to canned tuna.
Recent medical evidence reflects the desirability of decreasing the intake of sodium chloride, i.e. common table salt, in the human diet. With the ready availability of table salt as a seasoning and with the addition of table salt in many processed foods consumed in industrialized countries, a typical resident of such industrialized countries has a daily salt intake far and above their nutritional requirements. Indeed, the excess salt intake in industrialized countries contributes to poor health of their citizens because of the promotion of hypertension and other such maladies brought on by excess salt intake.
Monosodium glutamate, i.e. the sodium salt of glutamic acid, a major constituent of many proteins, is also used as a seasoning. Excess intake of monosodium glutamate has been indicated as being the cause of a syndrome commonly referred to as the Chinese Restaurant Syndrome. This syndrome is usually acquired after eating food which is seasoned with excessive amounts of monosodium glutamate.
Glutamic acid constitutes about 20% of the protein in soy protein. Acid hydrolysis of soy products typically liberates all the glutamic acid as a free amino acid. When the acid utilized for the acid hydrolysis is subsequently neutralized with an appropriate base, as for instance sodium hydroxide, the glutamic acid is converted to monosodium glutamate. Hydrochloric acid typically is used for the acid hydrolysis of soy protein. When this hydrochloric acid is neutralized, the chloride ion from the hydrochloric acid is converted to sodium chloride, i.e. common salt. Since protein derived from soy based products typically represents about 50% of that product, after acid hydrolysis and neutralization the hydrolyzed protein from a soy base product typically will contain 10% monosodium glutamate (derived from the 20% glutamic acid fraction of the protein) as well as large amounts of salt, up to about 50% by weight of salt.
When acid hydrolyzed vegetable protein is utilized as an additive to other food products, as for instance canned tuna, while the beneficial effects of the hydrolyzed vegetable protein are achieved, i.e. retention of the natural juices and the solubles therein within the tuna flesh, concurrently adverse properties can also be imparted to the canned tuna because of the increase of its salt content and the increase in the monosodium glutamate content. While tuna flesh itself contains an inherent amount of monosodium glutamate, as for instance about 0.25%, it is evident that the monosodium glutamate content of canned tuna will be significantly raised by adding a hydrolyzed vegetable protein since the hydrolyzed vegetable protein can contain up to 10% monosodium glutamate. Thus while the use of hydrolyzed vegetable protein as an additive to canned tuna contributes to a more desirable product with respect to taste, retention of natural juices and the like, it concurrently also contributes excess amounts of monosodium glutamate and sodium chloride which are counter indicated for health reasons.
It has also recently been found that certain mutagens can also be produced when vegetable protein is hydrolyzed in closed vessels under pressure. These mutagens are 1,3-dichloropropanol, commonly referred to as dichloropropanol, and 1-chloro-2-propanol and 3-chloro-l-propanol, commonly referred to as monochloropropanol. While the amounts of dichloropropanol and monochloropropanol found in typical hydrolyzed vegetable protein is very low, nevertheless minute traces are still found. When these minute traces are multiplied by the millions of pounds of hydrolyzed vegetable protein which is sold and consumed each year, the potential for adverse health effects inflected on the consumer by dichloropropanol and monochloropropanol is increased.